1. Field of the Invention
This invention relates to a vehicle steering control system.
2. Description of the Related Art
The assignee proposes, in Japanese Laid-Open Patent Application No. Hei 7 (1995)-47970, a vehicle steering control system which calculates a desired running behavior of the vehicle, more specifically a desired yaw rate of the vehicle based on the detected vehicle speed and steering angle with the use of a yaw rate model, and calculates a desired course of travel based on the calculated desired yaw rate such that the steering torque (steering force) is assisted in response to an error between the desired course of travel and the actual course of travel determined from the detected yaw rate.
In addition to the above, the assignee proposes in Japanese Laid-Open Patent Application No. Hei 5(1993)-197423 and Hei 9(1997)-221054 etc. vehicle steering control systems which photo-sense and output image signals of the road ahead of the vehicle to detect white lines (defining lane boundaries of the road) and provide steering angle assistance such that the vehicle runs along the detected white lines.
By providing fine steering assistance while preventing vehicle lane wandering, these technologies greatly reduce the burden on the vehicle driver, which tends to increase particularly during long, high-speed driving on an expressway or the like.
Aside from the above, the range of navigation systems extends to embrace everything from simple orientation aids to guidance systems featuring automatic route determination. The navigation system has a road-map memory stored in a CD ROM or the like, and detects the instantaneous vehicle position by, for example, the GPS (Global Positioning System) satellite position system, and provides directional information on a road map including the detected instantaneous vehicle position.